This application is a national stage application, according to Chapter II of the Patent Cooperation Treaty.
This is a filing of a national phase PCT application in the United States originating from PCT Application No. PCT/GB99/03977 filed Nov. 30, 1999 which claimed priority from United Kingdom Patent Application No. 9828291.6 filed Dec. 23, 1998.
The present invention concerns improvements in or relating to apparatus and methods for winding a cover yarn or yams around a core yarn. The method and apparatus especially, but not exclusively, is concerned with yarns ultimately to be knitted into hosiery, for example ladies stockings and tights.
U.S. Pat. No. 3,834,143 discloses a method and apparatus for covering a core yarn, in which a cover yarn is wound around the core yarn.
The relatively small diameter of the core and covering yarns and the relative fragility of the yams gives rise to certain difficulties. Prior apparatus and methods have overcome some of these difficulties but certain disadvantages remain.
In one presently accepted apparatus, cover yarn is pre-wound on to a specially shaped, doubled flanged bobbin which is mounted on a hollow spindle positioned between a core yarn supply and a core yarn take-up with the core yarn passing through the hollow spindle. Cover yarn is wound around the core yarn after it has passed through the hollow spindle by rotating the flanged bobbin. The maximum rotational speed of the bobbin is restricted by virtue of its mass and dimensions and this means that only a limited amount of cover yarn can be wound on to the core yarn if it is to achieve an acceptable rotational speed. The relatively small amount of cover yarn on the bobbin means that the apparatus has to be stopped frequently to change bobbins. The length of covered yarn taken up on the core yarn take-up is relatively short and, in practical terms, perhaps a quarter of the length of yarn normally carried by the yarn spools utilised on commercial knitting machines. To provide a spool of yarn for a commercial knitting machine it is therefore preferable to rewind the covered core yarn from several yarn take-up spools. Normally the contents of at least four take-up spools are wound onto the knitting machine package and this means that, in addition to the inconvenience of providing re-spooling machinery, providing man power to operate this re-spooling machinery and the replacement of bobbins in the covering machinery, the yarn supplied to the knitting machine includes knots at the joints between lengths.
According to one aspect of the present invention there is provided a method of covering a core yarn with a cover yarn comprising supplying a package of core yarn on a member which is fixed against rotation, supplying a package of cover yarn, guiding the cover yarn to form a loop which on rotation about an axis defines an envelope which surrounds the core yarn package, drawing off core yarn along the auras of rotation of the envelope in the direction away from the cover package so that when the core yarn intercepts the envelope it is covered by cover yarn.
Preferably a plurality of cover yarns are provided to form a multiple covering on the core, yarn, each cover yarn being taken from an independent supply of cover yarn, all of which are arranged in sequence on one side of the core yarn supply, the cover yarn from each supply being guided to form a loop which on rotation about an axis defines an envelope which surrounds the core yarn supply and all cover yarn supplies which are closer to the core yarn supply than the said cover yarn supply.
The loops are spaced from each other and rotated at the same speed and in the same direction.
Preferably all cover yarn envelopes are intercepted by the core yarn at the same point or closely spaced points. Preferably the loops which define all the envelopes are equally spaced angularly at the interception point.
According to a second aspect of the present invention there is provided apparatus for covering a core yarn comprising a mounting for a package of core yarn fixed against rotation, a first rotatable member located on one side of the core yarn package and a second rotatable member located on the other side of the core yarn package, the rotatable members being axially spaced from the core yarn package, means for rotating the first and second rotatable members at the same speed and direction, a mounting for a package of cover yarn, take-off means for leading cover yarn from said cover yarn package to the centre of said first rotatable member, first guide means in or on the first rotatable member for guiding cover yarn from the centre to or near to the periphery of said first rotatable member, second guide means in the first rotatable member for leading cover yarn from the first rotatable member to or near to the periphery of the second rotatable member, guide means in or on the second rotatable member for guiding cover yarn from or near to the periphery of the second rotatable member to the centre of the said rotatable member, core yarn take-off means for leading core yarn through the second rotatable member along its axis of rotation whereby cover yarn exiting from the second rotatable member at its centre is wound around the core yarn, and means for drawing off covered yarn.
Preferably the rotatable members are discs.
Preferably the mounting for the cover yarn package is fixed against rotation.
Preferably the guide means for the cover yarn in or on the second disc includes a guide closely adjacent to the aids of rotation of the disc such that cover yarn is wound around the core yarn from a direction generally perpendicular thereto.
Preferably the means for holding the core yarn packaging against rotation includes a magnet in the core yarn mounting and a magnet on a fixed member located on the side of the second disc opposite to said core yarn mounting.
Preferably a hollow member passes through the core yarn package through which core yarn from the package is guided to the centre of the second disc.
Preferably a yarn tensioner is provided for the core yarn.
Preferably the tensioner comprises first and second annular discs mounted for axial movement over the surface of the hollow member, a spring for biasing discs towards the end of the hollow member and an annular member resting on the disc closest to the end of the member, the weight of said annual member being variable to vary tension on yarn passing between the discs prior to it passing through the spindle.
Preferably the axes of the cover yarn package, the first and second disc and the core yarn package are coincident.
Preferably a cylindrical enclosure is provided around a pair of co-operating discs and the core yarn package, extending between members located on the sides of the discs remote from the core yarn package.
Preferably one or more additional cover yarn packages are interposed between the said cover yarn package and the core yarn package, each of said interposed packages having a pair of discs on each side thereof, with each disc being provided with cover yarn guide means for directing cover yarn from preceding package(s) from the centre to the periphery of the upper disc of the pair, from the periphery of the upper disc to the periphery of the lower disc, from the peripheral of the lower disc to the centre thereof and thereafter to the centre of the next succeeding discs with all the discs being rotated at the same speed and in the same direction.
Preferably each disc has guide paths for each cover yarn passing across the disc.
Preferably said paths are angularly equispaced.
Alternatively the apparatus includes a further mounting for a package of second cover yarn, means for holding the further mounting against rotation, third and fourth discs located on each side of the said mounting and package, means to rotate the third and fourth discs at the same speed and in the same direction, means for leading covered yarn from an earlier covering apparatus to the centre of the third disc, guide means in or on the third disc for guiding covered yarn from the centre to or near to the periphery of the third disc, means at or near the periphery of the third disc for guiding covered yarn to a point at or near the periphery of the fourth disc, guide means in or on the fourth disc for guiding covered yarn from its periphery to its centre, and further guide means for guiding covered yarn through the centre of the fourth disc whereby the second cover yarn and the covered yarn are wound together and means for drawing off covered yarn.
Preferably the guide passages are formed through each disc. Alternatively, they may be formed over a surface of the disc.
Preferably yarn guides are located at the ends of each passage, the yarn guides being formed from a hard wearing material, for example a ceramic material. Preferably yarn guides are mounted at a position spaced internally from the periphery of the disc.
According to a further aspect of the present invention there is provided a method of covering a core yarn with a cover yarn comprising removing core yarn from a package of core yarn fixed against rotation, drawing the core yarn through a hollow member, rotating first and second discs at the same speed, about the axis of said spindle with the discs spaced on either side of the core yarn package, supplying a cover yarn to the centre of the first disc, leading the cover yarn from the centre of the first disc to its periphery, then to the periphery of the second disc, then from the periphery of the second disc to the centre of the second disc, guiding core yarn through the centre of the second disc along the axis if rotation thereof, winding cover yarn around the core yarn and drawing off the covered core yarn.
A further aspect of the present invention provides a method for producing covered yarn in which a cover yarn is tensioned and guided radically away from the axis of a core yarn package, axially alongside the core yarn package and thereafter radially towards the axis of the core yarn package while being rotated about the said axis, core yarn being drawn off its package and along said axis whereby the cover yarn is wound around the care yarn after being guided towards it.
According to a still further aspect of the present invention there is provided a yarn tensioner comprising generally vertical hollow member, first and second discs mounted for axial movement along the member and adapted to receive the yarn to be tensioned therebetween, biasing means for urging the discs towards the top of the hollow member and an adjustable weight located on the upper disc.
Preferably the yarn is guided radially from the outside to the inside of the discs and thereafter along the hallow member to and over its top.
Another aspect of the present invention provides an enclosure for a yarn covering apparatus comprising a cylindrical member adapted to be arranged in an apparatus in which a loop of covering yarn is caused to rotate about a core yarn to be covered coaxial with and around the rotating loop of cover yarn and means for causing a rotational movement of the air within the enclosure in the same direction as the rotation of the loop and at a speed no greater than the loop speed.
Preferably the same means rotate the loop and the air.